1. Field of the Invention
The present invention relates to a resin-sealed semiconductor device for surface mounting and a method for manufacturing the same.
2. Description of the Related Art
The following is a description of a general method for manufacturing a resin-sealed semiconductor device, with reference to the accompanying drawings.
First, a metal sheet is processed into a desired shape of electrodes by etching or press working, thus producing a lead frame. FIGS. 14A and 14B show an example of the obtained lead frame, with FIG. 14A being a plan view and FIG. 14B showing a combinational cross-section taken stepwise along the alternate long and short dash line Axe2x80x94A in FIG. 14A seen in an arrow direction. In FIGS. 14A and 14B, numeral 900 denotes a frame, numeral 901 denotes a die pad on which a semiconductor chip is mounted, numeral 903 denotes bonding leads for a connection to the semiconductor chip, and numeral 910 denotes a pair of support leads for supporting the die pad 901 from both sides. As shown in the figure, the die pad 901 is displaced toward the side opposite to that on which the semiconductor chip is mounted with respect to a plane including the frame 900 and the bonding leads 903, so as to be depressed stepwise.
Next, as shown in FIGS. 15A and 15B, a semiconductor chip 950 is mounted on and bonded to the die pad 901 with an adhesive or the like. Then, a bonding pad of the semiconductor chip 950 and the bonding leads 903 are connected by wires 905 (wire-bonded). FIG. 15A is a plan view, and FIG. 15B shows a combinational cross-section taken stepwise along the alternate long and short dash line Axe2x80x94A in FIG. 15A seen in an arrow direction.
Subsequently, as shown in FIG. 16A, the semiconductor chip 950, the die pad 901 and the bonding leads 903 are sealed between an upper die 981 and a lower die 982. As shown in FIG. 16B, a sealing resin 990 is injected in an injection direction 991 to form a resin-seal, then the dies 981 and 982 are opened to obtain a semiconductor device. FIGS. 16A and 16B show combinational cross-sections taken stepwise along a line corresponding to the alternate long and short dash line Axe2x80x94A in FIGS. 14A and 15A seen in an arrow direction.
Semiconductor devices are required to have still higher performance, smaller size, thinner structure and more pins. For achieving higher performance, current-driven bipolar semiconductor chips, for example, come to be used widely. Since the semiconductor chips of this type generate a large amount of heat, they need to be designed considering their heat radiation. For this purpose, as shown in FIG. 16A, the die pad 901 is depressed with respect to the frame 900 such that the lower surface of the die pad 901 contacts an internal wall surface of the lower die 982. In this manner, after the resin-sealing, the lower surface of the die pad 901 is exposed to the lower surface of the semiconductor device. By packaging the semiconductor device so that this surface contacts closely to a circuit board, the heat generated by the semiconductor chip 950 can be conducted to the circuit board via the die pad 901 so as to be radiated.
For reducing the size and thickness of the semiconductor device and increasing the number of pins therein, it is desired that a metal sheet with which a lead frame is produced is made thinner and that the support lead 910 for supporting the die pad 901 is made narrower. However, this reduces the strength of the support lead 910. Consequently, as shown in FIG. 16B, when the resin is injected, the die pad 901 floats up due to a resin flow and a press shape of the support lead 910, so that the resin is injected also at the lower surface of the die pad 901. As a result, the lower surface of the die pad 901 cannot be exposed to the lower surface of the semiconductor device, making it impossible to radiate heat sufficiently from the semiconductor chip 950.
In addition, when the die pad 901 is displaced during the resin-sealing as described above, the semiconductor chip 950 mounted on the die pad 901 is somewhat distorted. Thus, if the die pad 901 is sealed while keeping the displacement, the semiconductor chip 950 maintains its distortion so that internal stress remains. This causes a change in the resistance of wiring in the semiconductor chip, leading to variations in characteristics. This also is a problem in those semiconductor devices in which the die pad 901 is not exposed to the lower surface of the semiconductor device because the heat-radiating characteristics are not as important.
Thus, it is an object of the present invention to prevent displacement of a die pad during a resin-sealing and residual distortion in a semiconductor chip, thereby providing a semiconductor device with a stable quality and the method for manufacturing the same.
In order to achieve the above-mentioned object, the present invention has the following structure.
A semiconductor device according to a first structure of the present invention includes a semiconductor chip, a die pad having a surface on which the semiconductor chip is mounted, and support leads formed in one piece with the die pad. The semiconductor chip, the die pad and the support leads are sealed with a resin. Protrusions are formed on the support leads on a same side as that of the die pad on which the semiconductor chip is mounted. With this structure, the protrusions provided in the support leads prevent the displacement of the die pad during the resin-sealing. Therefore, the die pad is arranged according to its initial design, making it possible to obtain the semiconductor device having the semiconductor chip in which distortion does not remain.
In the first semiconductor device described above, a second protrusion may be formed on a surface of the die pad opposite to that on which the semiconductor chip is mounted. With this structure, the protrusions (first protrusions) provided in the support leads and the second protrusion provided in the die pad can prevent the displacement of the die pad during the resin-sealing.
Also, in the first semiconductor device described above, it is preferable that tops of the first and second protrusions are formed close to a resin surface of the semiconductor device. It is especially preferable that the tops of the first and second protrusions are exposed to an outer surface of the semiconductor device. With this structure, these tops contact internal wall surfaces of dies for resin-sealing, thereby preventing the displacement of the die pad during the resin-sealing.
In addition, in the first semiconductor device described above, it is preferable that a surface of the die pad opposite to that on which the semiconductor chip is mounted is arranged close to a resin surface of the semiconductor device. It is especially preferable that that the surface of the die pad opposite to that on which the semiconductor chip is mounted is exposed to an outer surface of the semiconductor device. With this structure, heat generated by the semiconductor chip can be radiated easily via the die pad.
A method for manufacturing the semiconductor device according to a first structure of the present invention includes forming a die pad and support leads as one piece using a flat metal plate, as well as forming protrusions on a surface of the support leads, mounting a semiconductor chip on a surface of the die pad opposite to that on which the protrusions are formed, and enclosing the die pad, the support leads and the semiconductor chip in a die, so as to seal them with a resin while bringing the protrusions into contact with an internal wall surface of the die. With this structure, the protrusions provided in the support leads prevent the displacement of the die pad during the resin-sealing. Therefore, the die pad is arranged according to its initial design, making it possible to obtain the semiconductor device having the semiconductor chip in which distortion does not remain.
In the first method for manufacturing the semiconductor device described above, the resin-sealing can be performed while bringing a surface of the die pad opposite to that on which the semiconductor chip has been mounted into contact with an internal wall surface of the die. With this structure, it is possible to prevent the displacement of the die pad during the resin-sealing, so the distortion does not remain in the semiconductor chip. Also, the lower surface of the die pad can be exposed to the lower surface of the semiconductor device, thus obtaining a semiconductor device with excellent heat-radiating characteristics.
In the first method for manufacturing the semiconductor device described above, a second protrusion may be formed on a surface of the die pad opposite to that on which the semiconductor chip has been mounted, and the resin-sealing may be performed while bringing the second protrusion into contact with an internal wall surface of the die. With this structure, the protrusions (first protrusions) provided in the support leads and the second protrusion provided in the die pad can prevent the displacement of the die pad during the resin-sealing.
A semiconductor device according to a second structure of the present invention includes a semiconductor chip, a die pad having a surface on which the semiconductor chip is mounted, and support leads formed in one piece with the die pad. The semiconductor chip, the die pad and the support leads are sealed with a resin. The support leads are curved or bent in parallel to their longitudinal directions. With this structure, the bending strength of the support leads improves, thereby preventing the displacement of the die pad during the resin-sealing. Therefore, the die pad is arranged according to its initial design, making it possible to obtain the semiconductor device having the semiconductor chip in which distortion does not remain.
A semiconductor device according to a third structure of the present invention includes a semiconductor chip, a die pad having a surface on which the semiconductor chip is mounted, and support leads formed in one piece with the die pad. The semiconductor chip, the die pad and the support leads are sealed with a resin. A recess is formed on a periphery of a surface of the die pad opposite to the surface on which the semiconductor chip is mounted, and the surface opposite to that on which the semiconductor chip is mounted is arranged close to a resin surface of the semiconductor device. It is especially preferable that the surface of the die pad opposite to that on which the semiconductor chip is mounted is exposed to an outer surface of the semiconductor device. With this structure, it is possible to prevent the displacement of the die pad during the resin-sealing, so the distortion does not remain in the semiconductor chip. Also, it is possible to obtain a semiconductor device with excellent heat-radiating characteristics.
A method for manufacturing the semiconductor device according to a second structure of the present invention includes forming a die pad and support leads as one piece using a flat metal plate, forming a recess on a periphery of the die pad, mounting a semiconductor chip on a surface of the die pad opposite to that on which the recess is formed, and enclosing the die pad, the support leads and the semiconductor chip in a die, so as to seal them with a resin while bringing the surface of the die pad on which the recess has been formed into contact with an internal wall surface of the die. With this structure, it is possible to prevent the displacement of the die pad during the resin-sealing, so the distortion does not remain in the semiconductor chip. Also, the lower surface of the die pad can be exposed to the lower surface of the semiconductor device, thus obtaining the semiconductor device with excellent heat-radiating characteristics.
A semiconductor device according to a fourth structure of the present invention includes a semiconductor chip, a die pad having a surface on which the semiconductor chip is mounted, and support leads formed in one piece with the die pad. The semiconductor chip, the die pad and the support leads are sealed with a resin. A periphery of a surface of the die pad opposite to the surface on which the semiconductor chip is mounted is formed to protrude, and the protruding periphery is arranged close to a resin surface of the semiconductor device. It is especially preferable that the protruding periphery is exposed to an outer surface of the semiconductor device. With this structure, it is possible to prevent the displacement of the die pad during the resin-sealing, so the distortion does not remain in the semiconductor chip. Also, it is possible to obtain the semiconductor device with excellent heat-radiating characteristics.
A method for manufacturing the semiconductor device according to a third structure of the present invention includes forming a die pad and support leads as one piece using a flat metal plate, forming a protrusion on a periphery of the die pad, mounting a semiconductor chip on a surface of the die pad opposite to that on which the protrusion has been formed, and enclosing the die pad, the support leads and the semiconductor chip in a die, so as to seal them with a resin while bringing the protrusion of the die pad into contact with an internal wall surface of the die. With this structure, it is possible to prevent the displacement of the die pad during the resin-sealing, so the distortion does not remain in the semiconductor chip. Also, the protrusion of the die pad can be exposed to the lower surface of the semiconductor device, thus obtaining the semiconductor device with excellent heat-radiating characteristics.
A method for manufacturing the semiconductor device according to a fourth structure of the present invention includes forming a die pad and support leads as one piece using a flat metal plate, forming a recess on a periphery of the die pad, mounting a semiconductor chip on a surface of the die pad opposite to that on which the recess has been formed, and enclosing the die pad, the support leads and the semiconductor chip in a die, so as to seal them with a resin. A protrusion is formed on an internal wall surface of the die so as to face the recess, and the resin-sealing is performed while bringing the recess and the protrusion into contact with each other. With this structure, it is possible to prevent the displacement of the die pad during the resin-sealing, so the distortion does not remain in the semiconductor chip. Also, the lower surface of the die pad can be exposed to the lower surface of the semiconductor device, thus obtaining the semiconductor device with excellent heat-radiating characteristics.
In the fourth method for manufacturing the semiconductor device described above, it is preferable that spaces are formed between the recess and the die on outer and inner sides of the protrusion. With this structure, it is possible to prevent the displacement of the die pad during the resin-sealing in a more reliable manner.
In the fourth method for manufacturing the semiconductor device described above, it is preferable that a groove-like concavity is formed next to the protrusion on an inner side of the protrusion of the die. With this structure, it is possible to prevent the displacement and the deformation of the die pad during the resin-sealing in a more reliable manner. Also, it is possible to ease the machining accuracy of the recess of the die pad and the protrusion of the die.
A method for manufacturing the semiconductor device according to a fifth structure of the present invention includes forming a die pad and support leads as one piece using a flat metal plate, mounting a semiconductor chip on a surface of the die pad, and enclosing the die pad, the support leads and the semiconductor chip in a die, so as to seal them with a resin while sticking a surface of the die pad opposite to that on which the semiconductor chip has been mounted to an internal wall surface of the die. With this structure, it is possible to prevent the displacement of the die pad during the resin-sealing, so the distortion does not remain in the semiconductor chip. Also, the lower surface of the die pad can be exposed to the lower surface of the semiconductor device, thus obtaining the semiconductor device with excellent heat-radiating characteristics.
In the first to fourth semiconductor devices described above, the die pad may be displaced toward an opposite side of the surface on which the semiconductor chip is mounted with respect to the support leads. Also, in the first to fifth methods for manufacturing the semiconductor device described above, the die pad may be formed so as to be displaced toward an opposite side of the surface on which the semiconductor chip is mounted with respect to the support leads. With these structures, the surface of the die pad opposite to that on which the semiconductor chip is mounted can be arranged close to the resin surface of the semiconductor device more easily.